Looking to convert XLS to XLSX without installing any software? Change My File offers the best free XLS to XLSX converter online that helps you upgrade your old Excel files in just a few clicks. Whether you're handling work spreadsheets or personal data, converting Excel 97-2003 format files (.xls) to modern Excel (.xlsx) is now fast, secure, and hassle-free.

Why Use Our Free XLS to XLSX Converter?

Our online Excel converter is built for speed and simplicity. Here’s what sets us apart:

Instant Conversion – Upload your .xls file and get your .xlsx version in seconds.
No Software Needed – 100% web-based. Convert Excel files online from any device.
Safe & Secure – Your files are encrypted and deleted automatically after conversion.
Free to Use – No hidden fees or signup required. Unlimited conversions.
High Compatibility – Converted XLSX files work seamlessly with Excel 2010, 2013, 2016, 2019, and Microsoft 365.

How to Convert XLS to XLSX Online for Free?

Using Change My File is simple and efficient. Follow these 3 easy steps:

Upload Your XLS File – Click “Choose File” and select your old Excel file.
Start Conversion – Our system instantly converts your file to XLSX format.
Download XLSX File – Click “Download” to save your updated Excel file.

That’s it! No email required, no registration—just quick and easy Excel format conversion.

Best XLS to XLSX Converter for Professionals & Students

Whether you're working with legacy spreadsheets, dealing with large datasets, or sharing files with clients, using the best XLS to XLSX converter online ensures compatibility and security. Professionals, teachers, students, and business users worldwide trust Change My File for fast and accurate Excel conversions.

Benefits of Converting XLS to XLSX Format

Upgrading to the XLSX format offers a number of advantages:

Smaller File Size – XLSX uses compression, making your files lighter and faster to transfer.
Improved Security – XLSX files are less prone to corruption.
Enhanced Features – Use new Excel features like Power Query, slicers, and advanced formatting.
Cross-Platform Support – Full compatibility with modern spreadsheet apps and cloud storage.

Frequently Asked Questions

Is this XLS to XLSX converter free?

Yes. Our tool is 100% free with no limits on the number of conversions.

Can I convert large XLS files?

Absolutely! Our tool handles files of all sizes smoothly and efficiently.

Will the formatting and formulas be preserved?

Yes, your converted files retain original formatting, formulas, and data.

Is it safe to upload my Excel file?

Yes. All uploads are encrypted, and files are deleted after processing.

Convert Your XLS File to XLSX Now – Fast, Free & Reliable

Don’t let outdated file formats slow you down. Use Change My File – the best free XLS to XLSX converter online – and upgrade your spreadsheets instantly. No downloads, no watermarks, no limitations. Just fast and secure Excel file conversion.

Start converting your old Excel files now with our easy-to-use online XLS to XLSX converter – and boost your productivity!

Information about XLSX
File extension
xlsx
File category
Document file
Stands for
Microsoft Excel Open XML Spreadsheet
Developer
Microsoft
Overview
An XLSX is one of the components of Microsoft’s office suite and it is popularly known as Excel or spreadsheet. It is compatible with Windows, Android and iOS. It stores the data in worksheets and each worksheet comprises of a number of cells (boxes) that are organized in a grid of columns and rows. These cells in actual store the data and every cell has its own identity (numbered row and letter named column). This identification of each cell is used to write formulae and to perform other arithmetical operations. They can also refer to other cells to get the values. The data can be formatted in this the same way, as we do in Microsoft word. It may also contain charts, histograms and line graphs; etc and these can be displayed using three-dimensional graphics. Boxes can be auto-filled by just dragging and expanding the selection box which one wants to copy.
Technical description
It is the successor to XLS as this predecessor only stores data using a single binary file whereas XLSX uses Open XML format in which files and folders are stored separately under a ZIP compression. The graphs that are generated can be attached to the current sheet or can be added to the different sheet. Besides this, there are some add-ins which can be used in Excel sheets. It includes, Analysis ToolPak for Statistical and Engineering data analysis), Analysis ToolPak VBA (Visual basics of the application comes into act here), Euro Currency Tools (To convert and format Euro) and Solver Add-in (for optimization and equation solving). Furthermore, including Version 12.0 and later ones, can have 1048576 rows and 16384 columns.
Links
wikipedia.org